Move attachments to object storage
Per https://gitlab.com/gitlab-org/gitlab-ce/issues/26897#note_36167390, we should be moving attachments to object storage.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Per https://gitlab.com/gitlab-org/gitlab-ce/issues/26897#note_36167390, we should be moving attachments to object storage.